Hypertension is one of the most important underlying causes of morbidity and mortality in the US. Despite the existence of evidence-based hypertension guidelines, fewer than one in three patients (29 percent) with hypertension have their blood pressure under control. Though patients with hypertension often do not adhere to treatments, physician decisions have a significant role in this problem. Prompting patients to ask doctors specific questions has proven widely effective in improving preventive care, but its effect on blood pressure control has not been studied. We have developed a web-based program to be used by patients with high blood pressure before doctor visits. The program asks patients questions about their medications, their hypertension care and their blood pressure control. Based on these responses and guideline-based rules, patients are given personalized feedback. The feedback includes questions that the patient should consider asking their provider, such as "Would I benefit from keeping my systolic blood pressure less than 140?" along with supporting information and a link to a reputable website (e.g., NIH) for further reading on the topic. Given that patients tend to get tests and treatments that they ask their physicians for, the website is designed to activate patients to ask questions that lead to better blood pressure control. The main aim of the study is to test the efficacy of providing access to the hypertension module of the website. We will recruit primary care providers (26) and randomize them into two conditions, intervention (1C) and control (CC). Patients with hypertension (500), from each provider, will be recruited and given access to the hypertension module of the website (Intervention Condition) or the preventive services module (Control Condition), which serves as an active control condition. The primary outcome will be the percentage of patients in each group whose blood pressure is controlled, according to JNC7 criteria (<130/80 for patients with diabetes or chronic kidney disease, <140/90 for all other adults). We hypothesize that, after 12 months of access to the website, 60 percent of patients in the 1C will have their blood pressure controlled, compared to 40 percent of patients in the CC. Uncontrolled high blood pressure is one of the greatest threats to the public's health. This study seeks to test the effect of a web-based intervention that, by encouraging patient to ask specific questions during doctor visits, has the potential to improve blood pressure control. As three of four Americans now have access to the Internet, this intervention holds great promise for improving blood pressure control and for improving the public's health by improving the quality of care for other common, chronic illnesses.